Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-03-01
2003-12-16
Short, Patricia A. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C524S027000, C524S035000, C524S047000, C525S167000, C525S175000, C525S186000, C525S190000, C525S408000, C525S411000, C525S425000, C525S437000
Reexamination Certificate
active
06664333
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to cold-water responsive compositions and methods of manufacturing and using cold-water responsive compositions. The cold-water responsive compositions of the present invention have a wide range of cold-water responsiveness ranging from cold-water dispersible to cold-water weakenable. The cold-water responsive compositions of the present invention comprise a blend of a hydrolytically degradable polymer such as polylactic acid and at least one cold-water responsive polymer such as polyvinyl alcohol. The compositions of the present invention are responsive to water at ambient temperature and conditions are particularly suited for use in the manufacture of a variety of disposable products.
BACKGROUND OF THE INVENTION
Even though the amount of plastics used in a variety of consumer goods, packaging and medical articles has not significantly increased over the past twenty years, the common perception is that more and more plastics are filling up our landfills. Plastics offer many advantages over the more traditional wood, glass, paper, and metal articles including improved performance, comparable or decreased cost of manufacture and decreased transportation costs. Disposal of all waste materials, including food waste, packaging materials, medical waste into a typical landfill provides a relatively stable environment in which none of these materials is seen to decompose at an appreciable rate. Alternative waste disposal options are increasingly discussed and utilized to divert some fractions of waste from entombment. Examples of these alternatives include municipal solid waste composting, anaerobic digestion, enzymatic digestion, and waste water sewage treatment.
Much controversy is associated with the disposal of medical waste. Both government agencies and members of the public sector have been increasingly directing in-depth scrutiny toward this subject. Admittedly, concerns over the fate of materials contaminated with infectious substances are valid and proper measures to insure the safety of health care workers and the general public should be taken.
Currently, medical waste can be categorized into reusable and disposable. Categorization as to whether certain waste is reusable or disposable is customarily determined according to the material from which the article was constructed and the purpose for which the article was used.
After use, reusable medical articles are cleansed and sterilized under stringent conditions to ensure disinfection. In comparison, disposable medical articles are usually only used once, and even then, disposing procedures are not straightforward, rather they often involve several steps to safeguard against potential hazards. Typically, after use, disposable medical articles must be disinfected or sterilized, adding a significant cost prior to disposal into a specially designated landfill or waste incinerator. As a result, the disposal cost for the contaminated single use articles is quite high.
Despite the high cost of disposal, single use medical articles are desirable because of the assurance of clean, and uncontaminated equipment. Many times in the medical context, sterilization procedures conducted improperly can result in detrimental effects such as the transmission of infectious agents from one patient to another. Improper sterilization can also be disastrous in a laboratory setting, where, for example, contaminated equipment can ruin experiments resulting in tremendous costs of time and money.
Currently, disposable medical fabrics are generally composed of thermoplastic fibers such as polyethylene, polypropylene, polyesters, polyamides and acrylics. They are typically from 10 to 100 grams per square yard in weight and can be woven, knitted or otherwise formed by methods well known to those in the textile arts while the non-wovens can be thermobonded, hydroentangled, wet laid or needle punched and films can be formed by blow or cast extrusion or by solution casting.
The use of polymers for various disposable articles is widespread and well known in the art, In fact the heaviest use of polymers in the form of film and fibers occurs in the packaging and disposable article industries. Films and fibers employed in the packaging industry include those used in food and non-food packaging, merchandise bags and trash bags. In the disposable article industry, the general uses of polymers occurs in the construction of diapers, personal hygiene articles, surgical drapes and hospital gowns, instrument pads, bandages, and protective covers for various objects.
In light of depleting landfill space and inadequate disposal sites, there is a need for polymers, which are water responsive. Currently, although polymers such as polyethylene, polypropylene, polyethylene terephthlate, nylon, polystyrene, polyvinyl chloride and polyvinyldene chloride are popular for their superior extrusion and film and fiber making properties, these polymers are not water responsive. Furthermore, these polymers are generally non-compostable, which is undesirable from an environmental perspective.
Polymers and polymer blends have been developed which are generally considered to be water responsive. These are polymers, which purportedly have adequate properties to permit them to breakdown when exposed to conditions, which lead to composting. Examples of such arguably water responsive polymers include those made from polyethylene oxide, starch biopolymers and polyvinyl alcohol.
Although polymers extruded from these materials have been employed in film and fiber containing articles, many problems have been encountered with their use. Often the polymers are not completely water responsive or compostable. Furthermore, some water responsive polymers may also be unduly sensitive to water, either limiting the use of the polymer or requiring some type of surface treatment to the polymer, often rendering the polymer non-water responsive. Other polymers are undesirable because they have inadequate heat resistance for wide spread use.
Personal care products such as diapers, sanitary napkins, adult incontinence garments, and the like are generally constructed from a number of different components and materials. Such articles usually have some portion, usually the backing layer, constructed of a liquid repellent or non-water responsive polymer material. The non-water responsive material commonly used includes plastic materials such as polyethylene film or copolymers of ethylene and other polar and nonpolar monomers. The purpose of the non-water responsive layer is to minimize or prevent absorbed liquid that may, during use, exude from the absorbent and soil the user or adjacent clothing. The non-water responsive layer also has the advantage of allowing greater utilization of the absorbent capacity of the product.
Although such products are relatively inexpensive, sanitary and easy to use, disposal of a soiled product is not without its problems. Typically, the soiled products are disposed in a solid waste receptacle. This adds to solid waste disposal costs and presents health risks to persons who may come in contact with the soiled product. An ideal disposal alternative would be to use municipal sewage treatment and private residential septic systems by flushing the soiled product in a toilet. Products suited for disposal in sewage systems are termed “flushable.” While flushing such articles would be convenient, the non-water responsive material currently used in personal care products normally does not disintegrate in water. This tends to plug toilets and sewer pipes, frequently necessitating a visit from a plumber. At the municipal sewage treatment plant, the non-water responsive material may disrupt operations by plugging screens and causing sewage disposal problems. It therefore becomes necessary, although undesirable, to separate the barrier film material from the absorbent article prior to flushing.
In addition to the article itself, typically the packaging in which the disposable article is distributed is also made from a non-water responsive,
Schertz David Michael
Wang James Hongxue
Brinks Hofer Gilson & Lione
Kimberly--Clark Worldwide, Inc.
Short Patricia A.
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